Method of projecting motion pictures



" Dec. 24, 1946. F. WALLER EIAL 2,413,269

' 'mamonqr PROJECTING MOTION PICTURES Filed Feb. 1, 1944 6 Sheets-Sheet1 'f I V NTOR.

1946; F. WALLER EI'AL I ,4 3, 69

METHOD OF PROJE CTI NG MOTION PICTURES Filed Feb. 1, 1944 6 Sheets-Sheet2 Fla. 5

FIG1.4

' INVENTOR.

Dec. 24, 1946. v v F. WALLER EI'AL I 2,413,269

METHOD OF PROJECTING MOTION PICTURES Filed Feb. 1, 1944 e Sheets-Sheet 3Dec. 24, 1946. F. WALLER ETAL 2,413,269

' Q IETHOD 0F PROJECTI'NGIMO'I'IOIN PICTURES Filed Feb. 1, 1944 r 6Sheets-Sheet 4 24, 1946, I WALLER ETAL 2,413,269

METHOD OF PROJECTING MOTION PICTURES q Fi led Feb. '1. 1944 sSheets-Sheet 5 I I x 4/ 9 7 Willi/MM IVI/II/l/l/Ml 7 INVENTOR.

' Dec. 24,1946, F. WALLER ETAL 2,413,269

METHOD OF PROJECTING MOTION PICTURES Filed Feb. 1, 1944 s Sheets-Sheet eFleJo I N VEN TOR.

7 mggz Ba i/WM Patented Dec. 24, 1946 METHOD OF PROJECTING MOTIONPICTURES Fred Waller, Huntington, N. Y;, and Willis Robert r, Long Hill,Conn, assignors to The Vitarama Corporation, Huntington Station, N. Y.,a corporation of New York Application February 1, 1944, Serial No.520,592

ing motion pictures This invention relates to methods of project-'vision of what may be called ascanning method of projection in which abeam of light isscaused to move progressively across the area of thefilm frame being projected, so as to illuminate the film frameprogressively to project an image in successive increments across thescreen, and in which the film is advanced continuously (nonthe screen,and in such case, the gate will be pro-- vided with an aperture coveringan arc substantially equal to the arc of the projection area of thecurved screen on which the pictures are to be projected. Theoretically,the method is adapted to projection through a sate aperture of 180, oreven more, but in practice, it is seldom desirable to project over anarc exceeding 180, and due to mechanical limitations, and particularlyto interference with the projection beam and has as an object the pro-Claims. (01. ss-iaa) by the film guiding and feeding means located atthe ends of the gate, the usual gate aperture is somewhat less, as forexample, between 90 and It will be understood,pf-cdiirseithat in thefollowing description weus'e the term aperture in a broad sense to referto the spac th'liugh, which the l ght beam is allowed topass'througfithe film for projection purposes. In the followingdescription, we shall assume a typical gate intermittently), with themovement of the beam 10 aperture covering 120 of arc, and a cylindricalof light so coordinated with the continuous movescreen area of likeextent. ment of the film that each successive image is The light passingthrough the film and gate pr jected onto the screen as a stationaryimage aperture to project the film image onto the screen orghnriecugergiigi 1sn1:ii(1;t1pcul;zr1?"i grlllpillcablllii t; ptanis preferablyin the form of a relatively narrow a 8c n W c 1 1' beam lengthwise ofthe film, i. e. in the direcdesired to project an image onto a concavecurved 0 n of movement thereof t extends transscreen, as for exampleacyhndrical or spheric l versely across the full width of the film.Suitable screen and in which It IS desired to project an means such areflectors lenses or masks are pro- Image over f wifie are of saidScreen, say 90 vided for concentrating light emanating from a ar as:screame s ss a: beam v am is r0 ate 0 move aong e lm in e oram ic orwide angle projection it is evident that Same direction t t t m is movedthrough th ulrveoci ofe min e ac. requiring an extraordinarily high rateof move- 22 25 beam a u f s beams of the mm, a another Object of the maybe employed to scan successive fllm frames g i 1s i an expansion ashereinafter explained, and for each such beam, 8 5 5: 53 g g f z g gg ga suitable optical lens system is provided, rotatg rat of mov ment f thg k t 8 53 ing with its respective beam, to pick upand focus convenigntlimit: 0 8 ep M n on the screen the light passing through film.

Other objects and advantages of the inven- In i i order 23 3 g gz g glgg tion will appear hereinafter. image on o e screenl m e t b b Apreferred embodiment of the invention semovigg cerium 5 1 om i 3: lectedfor purposes of illustration is shown in serve be ween t e gu r mac y ethe accompanying drawings in which 30 through the gate, the angularvelocity of the Figure 1 is a perspective aiagmmmatic View light beam,the extent of are of the gate aper- Figures 2 to 8 inclusive are plandiagrammatic ture and he angular distance between-successive View filmframe centers when held in the curved gate. Figure 9 is a. verticalsection on the line 99 If we represent the angular velocity of the mm ofFigure 10 showing apparatus for practicing the 40 through the gate byVII the velocity of the light beam by V, the arc of the gate aperture bymethod of the invention, and

Figure 10 isatopplan View A and the angular distance between successiveAccording to the present inventionlthe fil frame centers by F, suchrelationships may be to be projected is fed continuously(not-intermitexpressed y the formula tently) through a curved gate orother suitable A curved film guide means adapted to hold the portion ofthe film to be projected in cylindrical shape. Normally, unless opticalcorrective means are provided, the center of curvature of the gate Thenear F f i i slccessive fraine should coincide with the center ofcurvature of centers can be lead y cu a of course or a curved gate ofany given radius.

Furthermore, the spacing between successive light beams must be properlyrelated to the other factors as above described. If we represent theangular distance between successive light beam centers by D, suchrelationship may be expressed by the formula 1 Applying these formulasto specific c'ondltlons,

it will be seen that if the gate aperture extends through an arc of 120apart. It the gate aperture remains 120, but

" the film frames are spacedfiat 90 between centers, the ratio of lightbeam velocity to fihn velocity will be four to one, and successive lightbeams should bespaced 360 apart, Likewise, if

the gate aperture remains 120 but the film ratio of light beam velocityto film velocity will be four to three and successive light beams shouldbe spaced 40 apart.

In practice, bearing in mind that the succes sive light beams are pickedup' and focused by suitable optical lens systems rotating with therespective light beams, it is advisable to select 4 factors such thatthe required angular distance between successive light beam centers iseither 360 or equally divisible into 360, as 30, 40, 60;

90, 120, or 180, for example, in order to avoid mechanicalcomplications. In such case the means for moving the light beams andthelens holder for the optical lens systems may be mounted to rotate onan axis concentric with the axis of the curved gate, with successivelight beams and successive optical lens systems equally spaced aboutsaid axis. In fact, a single lens system may be used reversibly to focustwo beams spaced Thus,'in the specific'embodiment of the inventionillustrated in the drawings, the gate aperture and projection area ofthe screen are shown as arcs of 120 and'the successive film frames arespaced 72? between centers. This provides a ratio of light beam velocityto film velocity orfive to: i

two and successive light beams should be spaced 180 apart.' Under theseconditions, with the beams moving faster than the' film each beam willscan one entire frame length ofyfilm in the gate while the beam ismoving the entire length of the gate aperture. For example, assuming thefilm at a position where the trailing edge of a given frame of film isin line with the entrance edge of the gate aperture and in line with thecenter or the beam of light, since the fihn frame occupies 72 of thegate aperture, it needs to move only 48 to bring its leading edge intoline with the exit edge of the gate aperture. Accordingly if the lightbeam moves at a rate bearing a ratio of five'to two to the rate ofmovement of the film, it will be apparent that bythe time the film hasmoved 48 the light beam will have moved 120, thus scanning the entirelength. of one film frame during such movement and projecting theimageof said filmframe progressively iii successive increments across the 120projection area of the screen Thus the 72 image of the film frame hasbeen expanded over 120 of arc of the screen.

.The image so projected onto the screenlwill appear thereon as astationary image despite the continuous motion of the film and thecontinuon motion of the beam of light, as will appear fromconsideration'of the diagrams of Figures 1 to 8 inclusive. In thediagram of Figure 1,

the elements essential for projection according tothe\method-of theinvention are shown in andthe successive film frames are spaced at 60between centers when 1 held in the curved gate, the-ratio oi light beam7 velocity to film velocity will be two to one, and successive lightbeams should be spaced 120 frames are spaced at 30 between centers, the

m to a, the film strip seemed over a feed sprocket 3 adapted to feed thefilm strip continuously at a constant rate. Between the guide roller 2and the feed sprocketB, thej'film strip passes through a curved gate(not shown structurally in these figures) which holds the orwith theaxisof .rotation 4 of the lens holder 5 containing a suitable opticallens system: do!

face of the curved screen 5. In the e'mb illustrated, the screen 6 isshown as having a cylindrical surface, and the axis of the cylinder alsoholder 5. The gate aperture is indicated diagrammatically by the spacebetween the members and 'l', which may be assumed to constitute the endsof the gate, and the annular aperture of the gate is assumed to be 120.Consequntly,

as illustrated, the arc ofthe projection screen 6 is also assumed tobe120.

The first film image frame to be projected lies between the lines A andE, and the-second illm image frame to be projected lies between thelines AA and EE, the latter of which coincides with the line A, asshown, For convenience, these two film image frames have-beencross-hatched in opposite directions on thedrawings so that "they may bereadily distinguishable,

As previously stated, Figures 1 and 2 illustrate the. positions of theelements at the beginning of projection'of film image frame AE,---and itwill a be observed that the trailing edge Acf said frame is in line withthe entrance edge of the gate aper- 5'ture, and the leading edge E atsaid frame is spaced 72 from the trailing edge. The entire iarea of thefirst frame, therefore, is exposed to ..the gate aperture.

light X used for projection purposes, and which is represented inFigures 1 to 8 by dot-dash oonstruction lines, is in position to.project through the trailing edge A of the first frame. There fore, thelight passing through the ortion of'the film image at this edge of theframe is received by the optical lens system'in. the lens holder 5, 1;

and is focused thereby on the screen A.

In Figure 3, the beam of light and the lens; j holder are assumed tohave rotated through an angle of 30, and bearing in mind that in theexample selected for purposes of illustration, the ratio of the angularvelocity of the beam to the angular velocity 33i the film in the gate isitssumed to be.;fto :2,-.it will be seen that the film will have a speed12 during such movement: of the lig t 'beam. Therefore, while progressinFigure 3, the light beam will have scanned 18 "of arc of the film frame,and will, at the stage illustrated in Figure 3, be projecting throughthe region B of the imageto form a projected image in the region B ofthe screen. In the meantime. the film image within the area between Aand B which has been scanned by the beam of light will have beenprojected onto the screen area be- 75. tween A and B.

by I. Said film passeslover a guide roller 2 and tion of the film to beprojected in cylindrical 5 form, with the axis of the cy e d n focusingthe projection beam on the concave surodimimt coincides with the centerof rotation 4 of the lens At this stage, the beamv of i from theposition of Figure 2 to the positionkof B'-C' and C'-D Thus, by the timethe beam of light has moved through 120 to reach the end of the gateaperture, it has scanned 72 of the frame, or the entire length of theframe, and has spread a projected image progressively in successiveincrements across 120 of arc of the screen. However, by using a. narrowbeam of light, each successive increment is perceived by the eye of theobserver as a stationary increment, and the image as a whole isperceived as a stationary image.

At the stage shown in Figure 6, therefore, the projection of the firstframe has been completed, but according to the formula previously given,the next successive lightbeam used for projection purposes should bespaced at 180 from the preceding beam. Therefore, there should be aninterval of 60 as measured by the rotation of the lens holder before theprojection of the next successive frame can begin. The necessity forthis interval under the conditions assumed will be apparent from Figure6, for although the projection of the first frame has been completed,the

-second frame is not yet in position for projection to begin, as itstrailing 'edge AA has not yet reached the entrance end of the gateaperture. Motion of the film is continued during this interval,therefore, as indicated in Figure 7 where the lens holder has moved anadditional 30, while the film has moved 'an additional 12. In Figure 8,the. lens holder has again moved an additional 30 and the film has movedan additional 12, thus causing the second frame AA-EE to occupy the sameposition as the first frame occupied in Figure 2. Therefore, a secondbeam of light, as indicated ,at X moves into projection position withthe lens holder and the projection process 1 is repeated as before.

In the embodiment illustrated, the optical system contained in the lensholder is assumed to be reversible so that the same optical lens systemmay be used to focus the successive beams onto the screen. 'In order toprovide a fiickerless image on the screen, the light beam and the lensholder should be rotated at a rate such as to pro- ;ject forty-eight ormore images onto the screen .Der second.

A more detailed illustration of apparatus for carrying out the method ofthe invention is illustrated in Figures 9 and 10. As illustrated, thefilm ll passes over the guide roller 22 and feed the film passes througha, curved gate consisting ofupper and lower guide channels 28 and 30having a 120 aperture therein between the sup ports 21 and 21 atthe-ends thereof. Illumlna tion for projection purposes is furnished bya.pair oftubes 3|, 3| mounted in suitable holders I2, 32 and havingreflectors, 33, 33' adapted to concentrate the light emanating from'saidtubes into arelatively narrow beam which is directed toward a conicalreflector 28, and from said refiector through the film and gateaperture. As illustrated, the tubes 3|, 3| and their holders. andreflectors are mounted on a shaft 34 supported for rotation in bearings35 and 36. Said lens shaft also carries a lens holder 25 containing asuitable optical lens system as previously de- 5 to 2 ratio hereinbeforereferred to, or any other desired ratio depending upon the conditionsde-- sired. The axis of rotation of the shaft 34 coincides with the axisof curvature of the gate and with the axis of the conical reflector.

Since each of the tubes is used to provide a projection beam during onlya portion of each complete rotation, a commutator 40 may be providedhaving a conducting segment 4| adapted to be engaged by brushes 42 and43 mounted on the respective tube holders and connected to therespective tubes. A suitable lead 44 is provided to the conductingsegment, and a.third brush 45, connected to lead 46, operates against abushing 41 on the end of the shaft. By this arrangement, and byadjusting the length of the conducting segment as desired, the tubes maybe illuminated only when they are in projecting position.

In the foregoing description, it will be understood that theexpansion'of the projected image on the screen, as previously described,will result in a distortion of a film image photographed in the normalmanner. Such distortion may be corrected, however, either by condensingthe image when photographing the same or in transferring from negativeto positive for projection purposes.

It will be understood that the invention may be variously modified andembodied within th scope of the subjoined claims.

We claim as our invention:

1. The method of projecting a stationary picture image onto a screenwhich comprises continuously advancing a film having a picture imageframe thereon through a curved gate having an aperture longer than saidframe, and projecting a beam of light which is shorter than said framethrough said frame and aperture to project an elemental part of the filmimage while rotating 45 said beam on an axis concentric with the axis ofcurvature of the film in the gate at an angular velocity sufilcientlygreater than the angular velocity of the film in the gate to cause saidbeam to scan the full' length of said frame while traversing the fulllength of said aperture.

2'. The method of projecting a stationary pic-' beam of light which isshorter than said frame through said frame and aperture to project anelemental part of the film image while rotating said beam on an axisconcentric with the axis of go-curvature of the film in the ,gate at anangular velocity sumciently greater than the angular velocity of thefilm in the gate to cause said beam to scan the full length of saidframe while traversing the full length of said aperture and ooordinatingthe movement of the beam of light withthe movement of the film to causethe beam of 11ght.;to project through the center of the film frame atthe center of said aperture.

3; The method of projecting a stationary picelemental part of the filmimage while rotating said beam on an axis concentric with the axis ofcurvature of the film in the gate and coordinating the movement of thebeam of light with the movement of the film to cause the beam of lightto project through the trailing edge of said frame at the entrance endof said aperture, through the center of said frame at the center of saidaperture and through the advancing edge of said frame at the exit edgeof said aperture.

4. The method of projecting a stationary picture image onto a screenwhich comprises continuously advancing a film having a picture imageframe thereon through a curved gate having an aperture longer than saidframe, and projecting a beam of light which is shorter than said framethrough said frame and aperture to project an elemental part of the filmimage while rotating said beam on an axis concentric with the axis ofcurvature of the film in the gate at an angular velocity suflicientlygreater than the angular velocity of the film in the gate to cause saidbeam to scan the full length of said frame while traversing the fulllength of said aperture and rotating' an optical lens system, in linewith said beam of light to focus the image scanned by said beam of lightonto a curved screen, said optical lens system being aligned with thetrailing end of a frame at the entrance end of said gate aperture tobegin projection of said frame, and being aligned with the advancing endof said frame at the exit end'of said gate aperture to complete theprojection. 7 y

5. The method of projecting. motion-pictures which comprisescontinuously advancing a film having a series of picture image framesthereon through a curved gate having an aperture longer than thedistance between successive picture image frame centers, and projectinga beam of light which is shorter than said frame through said film andaperture to project an elemental part of the film image while rotatingsaid beam of light on an axis concentric with the axis of curvature ofthe film in the gate at an angular velocity greater than the angularvelocity of the film in the gate to cause said'beam of light to scansuccessive frames.

6. The method of projecting motion pictures which comprises continuouslyadvancing a film having a series of picture image frames thereon througha curved gate having an aperture longer than the distance betweensuccessive picture image frame centers, projecting a beam of light whichis shorter than said frame through said film and aperture to project anelemental part of the film image while rotating said beam of light on anaxis concentric with the axis of curvature of the film in the gate at anangular velocity greater than the angular velocity of the film in thegate to cause said beam of light to scan successive frames andcoordinating the movement of the beam of light with the movement of thefilm to cause the beam of light to project through the center ofsuccessive film frames at the center of said gate.

7. The method of projecting motion pictures which comprises continuouslyadvancing a film having a series of picture image frames thereon througha curved gate having an aperture longer than the distance betweensuccessive picture image frame centers, projecting a beam of light whichis shorter than said frame through said film and aperture to project anelemental part of the film image while rotating said beam of light on anaxis concentric with the axis of curvature of the film in the gate at anangular velocity greater than the angularvelocity of the film in thegate to cause said beam of light to scan successive frames andmaintaining the ratio of the angular velocity of the beam of light tothe angular velocitylof said film equal to the ratio. of the arc of saidaperture to the arc of said aperture minus the angular distance betweencenters of successive film frames in said gate. u

8. The-method of projecting motion pictures which comprises continuouslyadvancing tigfilm having a series of picture image frames thereonthrough a curved gate having an aperture longer than the distancebetween successive picture image frame centers, projecting a beam oflight which is shorter than said frame through said film and aperture toproject an elemental part of the film image while rotating said beam oflight on an axis concentric with the axis of curvature of the film inthe gate at an angular velocity greater than the angular velocity of thefilm in the gate to cause said beam of light to scan successive framesand rotating an optical lens system in line with said beam of light tofocus the image of each frame scanned by said beam of light onto acurved screen, said optical lens sys tem being aligned with the trailingend 'of a frame at theentrance end of said gate aperture tobegin-projection of said frame, and being aligned with the advancing endof said frame at the exit'end of said gate aperture to complete theprojection.

9. The method of projecting motion pictures which comprises continuouslyadvancing a film having a series of picture image frames thereon througha curved gate having an aperture longer than the distance betweensuccessive picture image rame centers, projecting a plurality of spacedbeams of light, each of which is shorter than said frames, successivelythrough successive frames of said series and through said aperture toproject an elemental part of the film image while rotating said beams oflight on an axis concentric with the axis of curvature of the film in 45the gate at an angular velocity greater than the angular'velocity of thefilm in the gate to cause successive beams of light to I scan successiveframes, the angular distance between successive beams of light beingequal to the angular dis- 7 tance between successive frame centersmultiplied by the ratio of the angular velocity of said beams of lightto the angular velocity of the film in the gate.

10. The method of projecting motion pictures which comprisescontinuously advancing a film having a series of picture image framesthereon through a curved gate having an aperture longer than thedistance between successive picture image frame centers, projecting abeam of light which is shorter than said frame through said I c film andaperture to project an elemental part of the film image, and rotating anoptical lens system on an axiscoinciding with the axis of curvature ofsaid gate at an angular velocity greater than the angular velocity ofthe film in the gate to focus the projected image on the screen, saidoptical lens system being aligned with the trailing end of a frame atthe entrance end of said gate aperture to begin projection'of saidframe, and being aligned with the advancing end of said frame at theexit end of said gate aperture to complete the projection.

FRED WALLER. WILLIS ROBERT DRESSER.

